Servicing internal combustion engines used in automobiles, trucks, and other vehicles is an old art which has continuously advanced in complexity, requiring ever more sophisticated testing apparatus and analytical skills. As the design and operation of internal combustion engines has become more technologically sophisticated, the adjustment of variables has become increasingly more critical to achieve optimum engine performance. Furthermore, the requirements of environmental anti-pollution and energy conservation standards have demanded that the optimum performance of internal combustion engines be consistently and regularly achieved.
Accurate, reliable, and repeatable testing of internal combustion engines is thus necessary to determine whether optimum performance is achieved, and if not, to diagnose potential deficiencies in performance and to designate corrective measures.
Traditionally, a service mechanic has provided such evaluative, diagnostic and corrective analysis. The increasing sophistication of internal combustion engines and the multitude of diverse technological fields involved has made it more difficult, and increasingly more expensive, to train a technician having the requisite degree of skill to test, diagnose, and repair an internal combustion engine. And even a sufficiently skilled technician is confronted with differences in the types of engine configuration, ignition systems, and problems encountered.
Typically, a service technician will use so-called "diagnostic" apparatus which are known in the prior art for use in testing internal combustion engines and providing information on which a diagnosis of engine operating conditions can be based. Principally, these apparatus provide test information relating to the performance of engine systems and require the evaluation of data so that (1) performance deficiencies can be identified; (2) suitable adjustments made; and or (3) defective engine parts can be identified and replaced.
Examples of such testing apparatus include commercial equipment such as the 16-000 and 25-000 Series Engine Analyzers manufactured by Allen Group, Test Products Division, Kalamazoo, Mich. 49007. These engine analyzers provide means for taking thorough measurements under specified test conditions to allow the diagnosis of the various operating systems of an internal combustion engine. Means are included for running a battery of tests of pertinent engine operating parameters. Data collected for each test is recorded in a comprehensive "Diagnostic Report" so that a reliable guide of engine performance under different operating conditions is obtained. Beginning with hookup to the engine, the engine systems tested are: (1) starting, (2) charging, (3) primary, (4) timing, (5) secondary output, (6) performance, (7) carburetor and exhaust, and (8) carburetor adjustment. The collected data for each system test consists of manually recorded data derived from analog meter readings (e.g. volts, current, RPM, dwell, etc.) taken while the engine is operated under various conditions.
Computer operated testing apparatus has also been proposed, such as described by Aloysius T. Cashel, et al., in U.S. Pat. No. 4,125,894, issued Nov. 14, 1978 and entitled "Engine Test And Display Apparatus." This apparatus also allows a series of measurements of operating parameters of an internal combustion engine to be conducted. A readout of measured engine parameters is displayed in a digital format on the face of a CRT or on a "print out" instead of on a meter; comparative readings occurring under different operating circumstances may be simultaneously displayed. Even though such apparatus allows the programmed acquisition of engine performance data by digital means, the diagnosis of engine deficiencies and maladjustments yet remains the responsibility of the operating technician.
Upon the acquisition of predetermined test information, various diagnostic equations and instructional or diagnostic matrices have been employed as methods to aid the evaluation of measured engine parameters to identify defective engine components or to pinpoint problem areas. For example, diagnostic equations and matrices for use in connection with the aforementioned Allen Test Products 16-000 and 25-000 Series Engine Analyzers are set forth in Allen Test Programmed Training Course, a manual provided by the manufacturer which sets forth instructions for use of the test equipment and provides various analytical methods for consideration of the data which the test equipment generates. A typical example includes instructions in the Training Course manual with respect to "Starting Current" analysis which indicate that high current and low cranking voltage is usually caused by a defective starter. Another example is a diagnostic matrix showing the various combinations of evaluative "low", "good", "high" evaluations for cranking volts, engine speed, starter current and recovery voltage, which indicate designated "likely problem[s]".
An apparatus is described by Robert W. Arnston et al., in U.S. Pat. No. 4,128,005 issued Dec. 5, 1978 and entitled "Automated Engine Component Diagnositic Techinques," (this patent also refers to the apparatus of the aforementioned 4,125,894 patent), in which engine performance data that is acquired is compared according to a computer program against engine specifications; a relative evaluation of that measured data is next obtained, (i.e. "high," "within," "low"), in the form of coded signals. These relative evaluations are collected and stored and then analyzed in matrix format by the computer program according to an AND/OR matrix equation to identify defective engine components or operating areas. Such an apparatus essentially adapts the conventional diagnostic "matrix" to a computer which conducts a similar analysis of stored evaluative data after all pertinent tests of the engine are accomplished.
A deficiency in certain computerized prior art methods and apparatus is that their diagnostic capability is principally limited to "comparator" type evaluations based upon stored specifications. This "comparator" type of operation requires a completed data set, much like a manually recorded "Diagnostic Report," before analysis is conducted, and involves an AND/OR matrix equation for diagnosis which is a format that intrinsically may not be able to provide a reliable solution, and which may be exceedingly complex in its programming requirements if computer operation is desired.